Little is understood about which pts are at risk for therapy-associated acute myeloid leukemia. The reporter gene hprt has established sensitivity & specificity as a biomarker in lymphocytes for detecting in vivo somatic mutation due to chemotherapy. We recently developed methods to measure in vivo hprt somatic mutation in myeloid stem cells & to analyze the molecular nature of the mutations. We hypothesize that hprt in myeloid cells will reflect the specific mutational pressure of cytotoxic therapies that lead to tAML.